include/pybind11/type_caster_pyobject_ptr.h

0001 // Copyright (c) 2023 The pybind Community.
0002
0003 #pragma once
0004
0005 #include "detail/common.h"
0006 #include "detail/descr.h"
0007 #include "cast.h"
0008 #include "pytypes.h"
0009
0010 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
0011 PYBIND11_NAMESPACE_BEGIN(detail)
0012
0013 template <>
0014 class type_caster<PyObject> {
0015 public:
0016     static constexpr auto name = const_name("object"); // See discussion under PR #4601.
0017
0018     // This overload is purely to guard against accidents.
0019     template <typename T,
0020               detail::enable_if_t<!is_same_ignoring_cvref<T, PyObject *>::value, int> = 0>
0021     static handle cast(T &&, return_value_policy, handle /*parent*/) {
0022         static_assert(is_same_ignoring_cvref<T, PyObject *>::value,
0023                       "Invalid C++ type T for to-Python conversion (type_caster<PyObject>).");
0024         return nullptr; // Unreachable.
0025     }
0026
0027     static handle cast(PyObject *src, return_value_policy policy, handle /*parent*/) {
0028         if (src == nullptr) {
0029             throw error_already_set();
0030         }
0031         if (PyErr_Occurred()) {
0032             raise_from(PyExc_SystemError, "src != nullptr but PyErr_Occurred()");
0033             throw error_already_set();
0034         }
0035         if (policy == return_value_policy::take_ownership) {
0036             return src;
0037         }
0038         if (policy == return_value_policy::reference
0039             || policy == return_value_policy::automatic_reference) {
0040             return handle(src).inc_ref();
0041         }
0042         pybind11_fail("type_caster<PyObject>::cast(): unsupported return_value_policy: "
0043                       + std::to_string(static_cast<int>(policy)));
0044     }
0045
0046     bool load(handle src, bool) {
0047         value = reinterpret_borrow<object>(src);
0048         return true;
0049     }
0050
0051     template <typename T>
0052     using cast_op_type = PyObject *;
0053
0054     explicit operator PyObject *() { return value.ptr(); }
0055
0056 private:
0057     object value;
0058 };
0059
0060 PYBIND11_NAMESPACE_END(detail)
0061 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)